Pressure regulator for hydraulically controlled machine tools

Abstract

A pressure regulator for hydraulically controlled machine tools comprises a first directly controlled three-way pressure-regulating valve with which required work pressure can be set by a machine control system. In addition to a first surface, the control spool is provided with a second surface to which hydraulic fluid under the pressure at the pressure port can be applied by means of an externally controllable valve. This results in an additional force acting upon the control spool in the direction opposite to, or in the direction of, the force exerted by the elastic element on the control spool.

What is claimed is: 
     
       1. A pressure regulator for hydraulically controlled machine tools comprising: a first directly controlled three-way pressure-regulating valve with a housing including an inflow, an outflow and a pressure port for a hydraulic fluid, and with a control spool mounted therein which is movable back and forth between a first position connecting the inflow with the pressure port, a second position closing the pressure port and a third position connecting the pressure port with the outflow, with a constant pressure being settable at the pressure port, on the one hand, by a force being applied to the control spool by a biased elastic element in the direction of the position connecting the inflow with the pressure port, and, on the other hand, by the control spool having a first surface to which hydraulic fluid under the pressure at the pressure port is applied, by means of which a force counteracting the force of the elastic element acts upon the control spool, the control spool provided with a second surface to which the hydraulic fluid under the pressure at the pressure port can be applied by means of an externally controllable valve and, when applied, results in an additional force acting upon the control spool in the direction opposite to the force of the elastic element.   
     
     
       2. A pressure regulator as defined in claim 1, in which the control spool is provided with further surfaces to which the hydraulic fluid under the pressure at the pressure port (30) can be individually applied by means of controllable valves. 
     
     
       3. A pressure regulator as defined in claim 2 characterized in that: a second directly controlled three-way pressure-regulating valve with the same features as the first pressure-regulating valve is provided, in that:   the second pressure-regulating valve is connected in parallel with the first pressure-regulating valve, and in that:   in order to regulate the constant pressure, one of the pressure-regulating valves can be brought via switching elements into an active position and the other into an inactive position.   
     
     
       4. A pressure regulator as defined in claim 1 in which a second directly controlled three-way pressure-regulating valve with the same features as the first pressure-regulating valve is provided, in which: the second pressure-regulating valve is connected in parallel with the first pressure-regulating valve, and in which in order to regulate the constant pressure, one of the pressure-regulating valves can be brought via switching elements into an active position and the other into an inactive position. 
     
     
       5. A pressure regulator as defined in claim 4 in which: switchable directional valves are provided as switching elements between the inflow ports and the pressure ports of the pressure-regulating valves. 
     
     
       6. A pressure regulator as defined in claim 4 in which: the control spools have an inactive position corresponding to the inactive position of the pressure-regulating valves in which they close off the inflow, the outflow and the pressure port relative to one another, and in which: the switching elements comprise an actuating element associated with each control spool and enabling the control spool to be brought into the inactive position. 
     
     
       7. A pressure regulator as defined in claim 6 in which: the housing comprises stops against which the control spools are brought to rest in the inactive position by the actuating elements. 
     
     
       8. A pressure regulator as defined in claim 7 characterized in that: actuating pistons which are alternately hydraulically activatable via a directional valve are provided as actuating elements.   
     
     
       9. A pressure regulator as defined in claim 6 in which: actuating pistons which are alternatively hydraulically activatable via a directional valve are provided as actuating elements. 
     
     
       10. A pressure regulator as defined in claim 1 in which: the elastic element can be biased by deformation under different forces, and in which: a tensioning cylinder is provided to enable, in a manner controlled via valves, various biased positions to be established. 
     
     
       11. A pressure regulator as defined in claim 10 in which: the biased positions can be set by stops. 
     
     
       12. A pressure regulator as defined in claim 11 characterized in that: an absolute value of the bias of the elastic element in preselectable via adjustment members.   
     
     
       13. A pressure regulator as defined in claim 10 in which: the valves are in the form of locking valves which hold one valve position. 
     
     
       14. A pressure regulator as defined in claim 13 in which: the valves are adjustable via externally controllable magnets associated with each valve position. 
     
     
       15. A pressure regulator as defined in claim 1 in which: an absolute value of the bias of the elastic element is preselectable via adjustment members. 
     
     
       16. A pressure regulator as defined in claim 1 in which: the second surface is smaller than the first surface. 
     
     
       17. A pressure regulator for hydraulically controlled machine tools comprising: a first directly controlled three-way pressure-regulating valve with a housing including an inflow, an outflow and a pressure port for a hydraulic fluid, and with a control spool mounted therein which is movable back and forth between a first position connecting the inflow with the pressure port, a second position closing the pressure port and a third position connecting the pressure port with the outflow, with a constant pressure being settable at the pressure port, on the one hand, by a force being applied to the control spool by a biased elastic element in the direction of the position connecting the inflow with the pressure port, and, on the other hand, by the control spool having a first surface to which hydraulic fluid under the pressure at the pressure port is applied, by means of which a force counteracting the force of the elastic element acts upon the control spool, the control spool provided with a second surface to which the hydraulic fluid under the pressure at the pressure port can be applied by means of an externally controllable valve and, when applied, results in an additional force acting upon the control spool in the direction of the force of the elastic element.   
     
     
       18. A pressure regulator as defined in claim 17, in which the control spool is provided with further surfaces to which the hydraulic fluid under the pressure at the pressure port can be individually applied by means of controllable valves. 
     
     
       19. A pressure regulator as defined in claim 18, in which a second directly controlled three-way pressure-regulating valve with the same features as the first pressure-regulating valve is provided, the second pressure-regulating valve is connected in parallel with the first pressure-regulating valve, and, in order to regulate the constant pressure, one of the pressure-regulating valves can be brought via switching elements into an active position and the other into an inactive position. 
     
     
       20. A pressure regulator as defined in claim 17, in which a second directly controlled three-way pressure-regulating valve with the same features as the first pressure-regulating valve is provided, the second pressure-regulating valve is connected in parallel with the first pressure-regulating valve and, in order to regulate the constant pressure, one of the pressure-regulating valves can be brought via switching elements into an active position and the other into an inactive position. 
     
     
       21. A pressure regulator as defined in claim 20, in which switchable directional valves are provided as switching elements between the inflow ports and the pressure ports of the pressure-regulating valves. 
     
     
       22. A pressure regulator as defined in claim 20, in which the control spools have an inactive position corresponding to the inactive position of the pressure-regulating valves in which they close off the inflow, the outflow and the pressure port relative to one another, and the switching elements comprise an actuating element associated with each control spool and enabling the control spool to be brought into the inactive position. 
     
     
       23. A pressure regulator as defined in claim 22, in which the housing comprises stops against which the control spools are brought to rest in the inactive position by the actuating elements. 
     
     
       24. A pressure regulator as defined in claim 23, characterized in that actuating pistons which are alternatively hydraulically activatable via a directional valve are provided as actuating elements. 
     
     
       25. A pressure regulator as defined in claim 22, in which actuating pistons which are alternatively hydraulically ativatable via a directional valve are provided as actuating elements. 
     
     
       26. A pressure regulator as defined in claim 17, in which the elastic element can be biased by deformation under different forces, and a tensioning cylinder is provided to enable, in a manner controlled via valves, various biased positions to be established. 
     
     
       27. A pressure regulator as defined in claim 26, in which the biased positions can be set by stops. 
     
     
       28. A pressure regulator as defined in claim 27, in which an absolute value of the bias of the elastic element is preselectable via adjustment members. 
     
     
       29. A pressure regulator as defined in claim 17, in which an absolute value of the bias of the elastic element is preselectable via adjustment members. 
     
     
       30. A pressure regulator as defined in claim 17, in which the valves are in the form of locking valves which hold one valve position. 
     
     
       31. A pressure regulator as defined in claim 30, in which the valves are adjustable via externally controlled magnets associated with each valve position. 
     
     
       32. A pressure regulator as defined in claim 17, in which the second surface is smaller than the first surface.